HP 8153A - Adjusting the Power Supply

Pulse Width
2f.Lsto 0.6f.Ls
The pulse width decreases with increasing line
voltage from approximately 2f.Ls(at 110 Volts)
to approx. 0.6f.Ls (at 220 Volts).
•li the power supply tries to start but switches off and on again
repeatedly, it indicates a failure in one of the DC supplies.
Check the voltage suppression diodes A3 VS103, VS122, VS123,
and VS102 for a short.
• Start pulses with an amplitude from -0.5 Volt to + 12 Volt indicate
a missing regulation voltage or a short on A3 U103 from pin l to
pin 2. (U103 may be defective)
• Start pulses with an amplitude from -0.5 Volt to +10 Volt indicate
a defective A3 U103 (pin 3 and pin 4 shorted together).
• li no switching pulses are visible, check the signals at A3 U102 pin
3 and 2.
U102 pin 3 t -rT
250us -.J J1_5V
Figure 4-1. Pulse at U102 pin 3.
U102 pin 2
6V
30ms
Figure 4-2. Pulse at U102 pin 2.
li these pulses are present, the problem may be that A3 Q101 is
open.
No signals indicate a defective A3 U102
Adjusting the Power Supply
1. Remove the instrument housing (see "Removing the Instrument
Housing" in Chapter 3) ..
2. Connect the DVM to the ground and +5V testpoints (TP305 and
TP301) on the circuit side of the Al Processor Board (dose to the
rear panel).
3. Using an isolated adjustment screw driver adjust RV156 for a
+5.12V DVM reading.
Note
Potentiometer RV156 can be reached through the slots on the right
hand side of the instrument.
Troubleshooting 4-3